Yes you do need a new brake master cylinder. You also need to check the caliper hub. You might need to get the 320 hub when yo get the calipers. You also have to make sure that the the brakes are vented properely. If your 230E has solid rotors then that would mean it has no vents in the front bumper. If you switch to the 320, it has vented brakes and the bumper allows air in to cool them so you'll probably need a new bumper too.